Update agent_builder.py (microsoft#3469)

no more then -> no more than
#typo

Author: scenaristeur

autogen/agentchat/contrib/agent_builder.py

@@ -109,7 +109,7 @@ class AgentBuilder:
 """
 
     AGENT_NAME_PROMPT = """# Your task
-Suggest no more then {max_agents} experts with their name according to the following user requirement.
+Suggest no more than {max_agents} experts with their name according to the following user requirement.
 
 ## User requirement
 {task}